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Python Python Basics (2015) Logic in Python Try and Except

Daniel Petrov
Daniel Petrov
3,495 Points
Posted by Daniel Petrov
Daniel Petrov
3,495 Points

How to check if an argument of a function is an integer?

Struggling with this challenge. It works without the first line: def add(arg1, arg2): but I think it must be there. Also not sure if I have to use input at all as the arguments may come from anywhere else. There is also some issue with "return(None)" I think

trial.py 
def add(arg1, arg2):
    try:
        arg1 = int(input("Enter your first digit: "))
        arg2 = int(input("Enter your second digit: "))
    except ValueError:
        return(None)
    else: 
        return(float(arg1) + float(arg2))

2 Answers

Steven Parker
Steven Parker
231,271 Points
Steven Parker
Steven Parker
231,271 Points

Remember that the arguments are being passed in to the function, you won't need to input them, and since this challenge is all about floats, checking for or converting to integers will not be used.

Just move your float-add-return line into the try block, and you won't need an else. So it would look like this:

def add(arg1, arg2):
    try:
        return(float(arg1) + float(arg2))
    except ValueError:
        return(None)
Daniel Petrov
Daniel Petrov
3,495 Points
Daniel Petrov
Daniel Petrov
3,495 Points

Thanks Steven, the third part of the challenge is actually about making sure the arguments are integers.

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,454 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,454 Points

The short answer is 

isinstance( <var>, int )

The longer answer is, for this challenge, you don't have to use the input() function. The challenge grader will provide arguments when calling the function.

The other change is to convert to float instead of int

For your code change:

Edit: change to float from int

        arg1 = int(input("Enter your first digit: "))
        arg2 = int(input("Enter your second digit: "))
# to
        arg1 = float(arg1)
        arg2 = float(arg2)

If you wanted to test your code, you can call the function with arguments:

add(5, 2)
add("1", 5)
Daniel Petrov
Daniel Petrov
3,495 Points
Daniel Petrov
Daniel Petrov
3,495 Points

Thanks Chris, that is something I tried as well before but for some reason, it did not work:

def add(arg1, arg2):
    try:
        arg1 = int(arg1)
        arg2 = int(arg2)
    except ValueError:
        return(None)
    else:
        return(float(arg1) + float(arg2))

Is this what you mean?

Chris Freeman
Chris Freeman
Treehouse Moderator 68,454 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,454 Points

I've corrected my answer to use float. If int were used then actual float arguments would be converted to int first then back to float losing information.

Also, the conversion to float only needs to happen once making thereturn` simple

Your whole code should be:

def add(arg1, arg2):
    try:
        arg1 = float(arg1)
        arg2 = float(arg2)
    except ValueError:
        return None
    else:
        return arg1 + arg2

Note return does not need the parens.